I would like to remove the alternator and lead engine batteries in favor of lithium batteries, solar and shore power. See photo of the current alternator belt system. I would like to get a slight bump in fuel economy and power. Should I either:
- Replace the alternator with a dummy pulley of the same size and belt
- Reduce the length of the belt
The lead acid engine batteries will be replaced with a 400AH lithium LiFePo4 battery pack, which will be charged with either shore or solar power. The advantages are:
1. Faster starting: High-current starting capacity: 4000Amps
2. Backup 12 Volt coach battery, deep cycle. If the house battery goes down, there is a high-capacity alternate supply.
3. Maintenance-free
4. Lighter than lead batteries
5. Should last 20 years
6. Better performance of house systems: Water pump, heater, solenoids due to higher voltage: Constant 13.2 volts (3.3v x 4)
7. Much lower self-discharge
The four lithium cells will be charged and balanced by an iCharger 4010 duo intelligent battery charger. Alternators cannot charge and balance lithium cells and do not have the following features:
1. Intelligent charge with full cell charging limit.
2. Storage charge. This charges to 50% SOC (State of Charge) and is good for long-term rig storage.
3. Test cell capacity (Amp Hours).
4. Bottom cell balancing and charging.
6. Charge on shore or solar power from the inverter.
Your advice is welcomed.
See photos.
Your alternator uses just a few HP at max output.
There are four step alernator controls that work with every type of battery including Lithium. Look at the ProRegU specs
https://baymarinesupply.com/media/downloadable/Sterling/ProRegulator.pdf
While I do NOT agree with taking the alternator out of the charging equation, were that my desire, I would leave the alternator in place and electrically disconnect it. Using it as an "idler" would would take close to zero HP and leave you with the option of reconnecting it if you change your mind.
Approx 2.5 hp at full output. Redundancy is a key feature on these coaches, why eliminate one? Nuclear winter, zombie apocalypse, you might need it.
Thanks for the advice. No alternators can safely charge lithium batteries because they do not know about lithium voltages and do not monitor all four cells. Plus, it shortens the life of lithium cells to keep them at 100% SOC when in storage. The ProRegU is only for lead batteries.
Guess it would be good to leave the alternator in place in case this experiment fails, or the next owner wants to change back to lead.
If we have an apocalypse, the solar system will still function after running out of diesel. The genny could also charge the engine battery with my proposed system.
Drive at night without generator running, you will quickly learn how important the alternator was. Headlights, dash heater a/c fan running on high and engine all will drain your start batteries. Cannot always count on solar during the day.
Please look more closely at the ProRegU. It clearly has settings for Lithium batteries. Call Alan at Bay Marine and ask him for more details or perhaps another suggestion.
Having no charging system other than solar, land line or generator seems like a disaster waiting to happen. DWMYH.
Balmar MC-614 is another regulator that has adjustable settings. I've used that one on my Newell with 1000AH LiFePO4 system, house batteries only. I don't remember the settings but basically had to dial it down so the max voltage was compatible. Also you have to limit the amps so you don't damage the alternator.
Repurpose the alternator into a regenerative braking device (easy) and be the coolest kid on the techno block
Tim,
May I suggest 4/0 cable from battey positive to starter and 4/0 cable from battery negative to engine block. Big wire for big cranking amps. These cables may be on current starting batteries and can be repurposed. I had less than 4/0 on my coach and changed my cables to 4/0.
Hope this helps. All the best and much success on your project.
Only issue I ran across is that li-ion batteries do not output power quickly.
My dirt engines would turn over slowly. Required turning on the headlight for a few minutes to build voltage up enough to start the motor.
Different chemistry. Not the most power output until used a bit.
While I am a BIG fan of LiFepo4 battery tech, and bought this coach precisely due to it having it, and solar, I would not take out the alternator EVER. The BMS system will keep the batteries from overcharging, and I would not EVER install a LiFepo4 bank without one. Witht the coast of lithium, not sure it makes sense to sub it out for lead acid for starting. If you really wanted to lose the weight of the lead, and really on a coach this size, whats the difference.... Get some capacitors for starting and have the boost set up to pair it with your house bank if needed. You will need the power when driving down the road. And there will be times when solar isn't there.
But if you really want lithium for starting battery, keep the alternator and set the bms up so they don't overcharge.
Bob
Leave the alternator. Get a smart or adjustable regulator. Common in marine applications.
Another option is to have a manual disconnect switch (Perko ON-OFF switch) between battery isolator and house bank that isolates the house batteries while driving. Probably the simplest solution. Could be installed at base of bed where it could be easily accessed.
Thanks for your feedback and making me think before I leap. I used to be a mediocre power supply design engineer, so forgive my nit-picking. Two major points, A and B below:
A. No practical smart chargers for lithium
There are no all-in-one lithium alternator regulators on the market that meet my requirements. I researched many regulators, including the Smart Charge R210A and Balmar MC-614. None pass requirements needed to safely charge and store LiFePo4 batteries for the following reasons:
The R210A and the Balmar MC-614 are admirable voltage regulators for lead-acid batteries. However, they appears to be a jury-rig for LFP batteries because they regulate voltage, not current. LiFePo4 batteries will draw excessive current at a constant voltage. They do not have three crucial features:
SHORTCOMINGS OF SO-CALLED "SMART' LITHIUM REGULATORS
1. No Current Detection
A constant current charge is required. A current shunt and a current adjustment is required. Regulating current by sensing the temperature of the alternator, then throttling field current based on temperature could cause an over-current condition when the alternator is cold. I would design the system with a Hall-Effect current sensor to replace the old fashioned shunt. Here is an excerpt of the PDF of the LFP algorithms:
9. LFP Constant Volatage 14.5 volts 30min then 13.4 volt rest voltage. C.V. time 20min.
0. LFP Constant Strait 13.4 volt cruiser voltage.
Both of these have constant voltage. They should have contsant current algorithms.
2. Over-voltage limit at the individual cell level
Sensing the voltage of all four cells is a "must have" because one cell will go over-voltage before the rest, thereby damaging the cell.
3. Cannot limit SOC
When the rig is shut down and put in storage, the SOC must be between 50% and 80% to maximize longevity of these expensive cells. This should be user-selectable.
See https://www.bruceschwab.com/wp-content/uploads/sites/86/2014/02/170928-Smart-Charge-R210a.pdf
The regulator companies need to hire competent engineers skilled in lithium chemistry, safety, sustainability and longevity. No offense is intended. These companies are hanging on to 200 year-old lead-acid technology, which is primarily charges using voltage sensing. An alternator regulator with a built-in current detection and BMS is needed.
I ran into this mentality with an engineer at Morningstar, the solar charger company. They refuse to see that lithium batteries can be damaged using lead-acid algorithms. My lithium batteries were damaged by a Morningstar controller because it could not detect over-voltage in several of my 16 cells. Cost me $400 to replace the bulging cells.
B. NEED TO CHARGE WHILE DRIVING
I agree with commenters that eliminating the alternator may cause unforeseen issues. Worst case watt-hour analysis of engine battery power requirements (watt hours) and rough KWH estimate include:
- Drive for 14 hours at night
- All lights on (30A x 14hr x 12v=5.04KWH) (Time to get LED headlights!)
- All accessories on (blower, radio, AC) (10A x 14hr x 12v=1.68KWH)
Total=6.72KWH This is a 1.9KWH deficit.
Although I do not have certainty about the above power calculation, the loads could likely exceed the 400AH, or 4.8KWH battery capacity. But since the engine battery will now be charged with the inverter using the 48Volt 9.4KWH house battery or the generator while en route if required. I do not see an issue, especially if LED lights are installed.
PS: I like the comment about regenerative braking. Ha ha. How about a wind generator?
Suspect this was posted as a joke-- wind resistance while driving would well exceed power output.
Said another way no device, and particularly a wind generator is close to 100% efficient.
So If I read this correctly, you pretty much made up your mind to do this before you asked the question. Fair enough. You are going to an all Lithium battery setup with no alternator where all of the lithium batteries can only be charged by land line or solar. (I asume you can use a generator to drive some acceptable charger to charge the batteries.)
I find it very hard to accept that there is absolutely no alternator charging solution for Lithium batteries. Maybe what you should do is replace the alternator with an engine driven 120v generator that can drive your acceptable 120v charger.
Have you ever considered that your system as you designed it is leading you down paths for which there are no solutions (acceptable to you) to the problems you create? Sort of like painting yourself into a corner.
Good idea about the 120 VAC alternator. Thanks! I will investigate it.
I want to do this project because:
1. Bought the 400AH lithium batteries at 70% discount. Long story.
2. In my reirement, I am a solution looking for a problem, even if there was no problem in the first place.
3. Would like to be a leader in new battery and green technology.
4. Would like to debunk most of the quackery about lithium battery maintenance and sustainability on the Internet.
5. Companies are making a killing off of inexperienced lithium battery customers and I would like to assist these buyers, sort of like Ralph Nader.
We have run our lithium system for about 18 months now. We currently have 1180 on top and 400A of storage. I did not want two different battery types using a common charger although Victrons Cyrix is available. I chose to isolate the two battery banks by using a simple marine switch. I have also set up the genset to fire off of either bank. Standard is chassis.
I have yet to have any charging issues requiring using the alternator to charge our house bank but in an emergency it is available. The rapid recovery, no absorption phase, lithium provides probably is part of the equation.
I also created a much more capable boost circuit if needed. I don't know your system nor am I an engineer but there may be a more simple system that allows you to keep the alternator and still meet most of your objectives. Good luck!
Do your lithium batteries have a built-in BMS?
Mine do not, so I plan on using an advanced RC charger, the iCharger 4010, to act as a BMS. It has many cool functions:
- Charging at selectable current and voltage settings
- Balancing cells, bottom or top method
- Storage charge, to maximize longevity. This is a must-have feature, since storing lithium batteries at 100% SOC can shorten their life.
See iCharger 4010Duo - ProgressiveRC (https://www.progressiverc.com/icharger-4010duo.html)
Bob (post #11 above) just bought a coach with Lithium battery "conversion".
Might get together with him and perhaps the previous owner who designed and installed the system.
I have a racer bud that is my EE go to guy. He is the lead engineer on a few electric race vehicles. I will put him onto this thread and see if he may be interested in assisting.
I asked Alan Ferber at Bay Marine Supply if it is possible to charge Lithium batteries with the alternator.
Here is what he said ...
"It is definitely possible to charge a lithium [with] a regulated alternator, you just set the voltages appropriately and cut the absorption period to a minimum. The problem with smart regulators is that newer cars need to set their own voltages, otherwise the vehicle's computer thinks there's an error. That's where Sterling's alt-to-battery and battery-to-battery chargers come in, since they leave the vehicle's voltages alone. On boats, with diesels and no engine control module, we use smart regulators.
In the end, lithium does fine on an AGM profile. Just set the absorption period short. And if it's a vehicle that's not running 24 hr a day, it's even less of an issue."
The solutions available to complex problems usually start with an open mind.
SO, from a practical/cost effective standpoint, if one uses two things will this work:
Smart regulator-- been available for decades for the marine industry.
If the smart regulator does not allow for a time-limiting factor: Mechanical ON-OFF switch to shut off charging to the LI batteries after XX hours of charging/driving.
Brett, I think that is right. Not every system is going to be completely automatic. In the end they all need the attention of a conscientious user whose goal is continuous learning. This is an evolving battery technology in a mobile installation in a wide range of temperatures. I think it is simply going to continue to improve. I am looking forward to what comes.
Technomadia has an interesting read on this subject, when they converted their batteries, not for sure if they are the same type.
http://www.technomadia.com/lithium/
You could use a MC-614-H by BALMAR to keep them charged. You MUST use a BMS for LiFepo4. The Balmar will have to be set up for it using the advanced settings.
The lithium system my coach has is all Victron with the BMS built in. Expensive. The Lithium system he is building is Chinese calb cells or similar. Not bad but must use a good bms. Again, though, not sure why you need to complicate the situation. Put all your lithium into a house bank charged by a good solar controller and inverter/charger. Put in some agms or gels for starting batt. Your good to go. Want to get fancy, put in some big capacitors. Engine start capacitors (http://www.maxwell.com/esm/) MAXWELL ULTRA31/1800 GROUP 31 12V ENGINE START MODULE ESM BATTERY 1800 CCA $1050 plus shipping but its only 21 lbs..
Or go with nice agm like NorthStar Group 31 AGM 1150 CCA NorthStar (https://www.impactbattery.com/nsb-agm31a.html?gclid=EAIaIQobChMItaKile3F2wIVA3ZeCh3wJwCXEAkYDyABEgKHg_D_BwE) $750 plus shipping. but its 152 lbs! So for a few more bucks the Maxwell ultraCapacitor will get you a great cranking battery that recharges in minutes, Will crank your engine without a problem. Keep your alternator to run things when the engine is going.
I would go with the Maxwell.
Bob
They are essentially the same battery. And they ruined them by not placing in a more controlled environment. Lithium batteries don't like to be too hot, or to cold, like Goldilocks, they want to be juuuussssttt right. More finicky for sure over gel or agm, but you get batteries that over its life cycle will get you more cycles, which means less moolah in the long term, Better performance, and longer life time, lighter too. But you have to pay attention. Many will say "they cost to much" but that is kind of funny considering some of those same people will pay >110K$ for a coach, 20K for a full paint job, and such. But in the end, its just money, you can't take it with you, and your kids will just blow it on stupid stuff, so make yourself happy and get what you want. I have been running the front air conditioner off my lithium's until put in the shore power at my house. It will run for several hours with the solar putting out 1100 watts or so. Can't do that on lead acid. And that doesn't use all the capacity. Also lithium has more usable amps than any other battery technology atm. So a 600 amp hour bank will give you 480 amp hours of usable capacity. To get that with lead acid you need well over 1100 amp hours. Its very difficult to put in the last amps on a lead acid setup, but not with lithium. and if you go below 50 % SOC with lead acid, you shorten its life span significantly. Not so with lithium. You can go down to 20%.
The firefly battery is the only lead acid tech that I would consider, but they are not cheap either.
But still, you can get my with good old trojan T105s golf cart batteries and call it a day, replace them every 4 years or so and be ok. Just not for me. Unless these blow up or something.....
The temp control as was stated would be a hard to overcome issue for most in my opinion.
Would seem to require an interior relocation and to need continious temp moderation.
That need was the main reason why I did not purchase a li-ion system five years ago.
We are not pedestal to pedestal users. Or like the gen on 24/7.
But a lot of owners do have temp controls on all the time. Maybe a good item for them.
I read Technomadia's article and incorporated their lessons about LFP batteries:
- Temperature control
- SOC control
The problem with today's smart regulators is that they do not address SOC control at the CELL level:
SMART REGULATOR SHORTCOMINGS WHEN CHARGING LFP BATTERIES
1. Use alternator temperature and voltage to regulate current.
I do not want to:
— Heat up the alternator
— Dump 100+Amps into the charging circuit
— Stress the alternator belt and bearings
— Increase fuel consumption
2. Can overcharge / damage one or more LFP cells
3. Cannot balance charge, which provides better performance.
4. Cannot "storage" charge, which increases longevity. Lithium batteries should be stored at 50% SOC.
— When a trip is planned, my iCharger 4010 will be set to fully charge the batteries from shore or solar power.
Thanks for the suggestions. There are some smart LFP batteries on the market that would charge from an alternator, but their price is about 8x of my proposed solution.
My electric bike shop in Solana beach,ca builds individual cell BMS for li ion battery packs for the San Diego rickshaw owners that ride tourists around. I watched a controller he made up slowly turn off individual led's on a panel denoting that group of cells was done being balanced. I think he was doing three cells at once.
Tim a good bms will do what your looking for.
Tim in answer to your earlier question. Yes I do have a BMS. I too installed an all Victron system which has individual cell management built into each battery and then connected to a Victron BMS. I wanted a fully integrated system that did not require trouble shooting conflicts across multiple vendors. AM Solar has created a temperature control board and I am attaching the schematic.. My battery's are on the original battery rack so air flows over and around them. They are not boxed in. Temperatures are monitored both within the battery and in the compartment. The battery compartment is directly under the couch so I am looking at providing cooling directly from the coach before we head west later this summer. Fumes are no longer an issue.
As to the Technomedia article, cutting edge single installs may or may not be dispositive of other systems. They did not ruin their battery's as in no longer usable but did shorten their life cycle. When I installed these almost two years ago, I was hoping for a horizon of 8 years or 76 years of age on the old man. At the present rate they should have more than half their cycles ahead of them. We enjoy their capabilities especially the charge profile and how nicely they compliment solar.
Note the schematic is the entire system. 1180 solar with 85 controller, 702 battery monitor, 3000 Multipass inverter with control panel, CCGX color monitor, Lynx bar and for me two 200AH battery's. Only two control boards are lithium specific.
You might find this of interest.
Advanced ICs Simplify Accurate State-of-Charge | DigiKey (https://www.digikey.com/en/articles/techzone/2013/jan/advanced-ics-simplify-accurate-state-of-charge-measurement-for-lithium-ion-batteries)
Lots of links and info for bms from modules to component level.
It's true that there's no trivial plug-and-play alternator option. You can definitely turn on and off your alt with a BMS, though. You sound like you're up for the project!
In my coach, I retained the engine lead-acid batteries and the alt. I charge the house lithium pack off the solar/power pole/genset. The lithium pack feeds a small lead-acid charger that keeps the engine start batteries topped off when at rest. Really easy and works great. Also, easy to revert back to a standard (boring) all-lead-acid config if the next owner doesn't want my custom electrical setup. (But I bet they will, because I can run the roof airs for days before I have to start the generator... whoohoo!)
The 12V, 2200 CCA engine lead-acid battery does three things:
- Starts the engine
- Starts the generator (I rewired my coach)
- Backup for the house 12 volt appliances
When I found these 400AH lithiums at 70% off, my brain creaked and fired off another project: the "Get rid of the Lead' project. The devil is in the details. Current generation of alternators, regulators and Lithiums are not compatible. Lithium batteries, as well as lead-acid for that matter, require a computer to calculate and store SOC (State of Charge) in memory. SOC can then be managed over a consistent time period. Alternators provide intermittent charge with no SOC management. That said, my main concern is about storage SOC:
MY SOC REQUIREMENT
- Lead acid: 100% SOC in "Storage Mode"
- Lithium: 50% SOC in "Storage Mode"
- No overcharging of any cell
There are no alternator chargers or commercial chargers that meet the lithium requirement except the iCharger 4010. Even this charger does not know SOC, but it knows charge and discharge current. I will experiment with it's "Storage Charge" mode to determine the SOC when it completes it's Storage Mode.
The problem is that charger manufacturers got away with over-charging lead-acid batteries for the last 150 years. Lithiums cannot tolerate over-charging and will degrade if stored at 100% SOC. This mind set is hard to change, bit still prevails, even at cutting-edge companies like Victron, Magnum and Morningstar. Their algorithms charge to 100%. This is not good for storing lithium batteries.
By the way, the Nissan Leaf has a charge feature where the battery can be charged to 80% SOC. This is the first intelligent charger that actually makes sense.
[/quote]
Love to hear about your coach and your setup, running roof airs for days is very impressive.
I've followed electric vehicles for over 40 years since being a northern California VW dealer selling the Citicar in 1977. I've owned more than several Toyota Prius vehicles last year and have to say, this is the best vehicle I've owned including those that cost over $70,000 to me new. All the German VW people transporters at German airports were all electric in the 70's. VW has done so much research, always saying their limiting technology was the batteries. Toyota has a new battery system supposedly coming out in 2020. I see another Prius in my future after I get more miles under my belt in the Foretravel. I have enjoyed following this electric thread. My budget and needs now include a simple 560 watt system with 2 8D AGM's and a new Xantrex Freedom SW 2012 Inverter/Charger. A thank you out to Dan AC7880 who sold me his core batteries when he updated to his new batteries.
Citicar - Wikipedia (https://en.wikipedia.org/wiki/Citicar)
The 400 amp hour lithium engine battery pack is installed and functioning. Starts the engine in one second. Here are some photos of the project. I have disconnected the alternator and am charging the batteries using a 115VAC to 12VDC IOTA supply powered by shore, genny or solar power. This powers the truely intelligent charger, iCharger model 4010 Duo.
Here are some salient points:
- Mounted inside coach for thermal regulation
- Intelligent, simple, no-hype LIFEPO4 charger that I can actually manage the batteries in terms of charge, storage and measuring Amp Hour capacity
- Found out the batteries are eight years old and still have their original capacity. They were new old stock for $550.
- The load on the batteries is 56mA with the battery disconnect switch off, 12A under daylight driving, 24A with the lights on and 37A with the defroster on full.
- Still have to do some carpentry to cover the system and make it look nice for the wife.
- Backup power: See photo for a schematic of my proposed silicon and schottky diode-based house 12 V house power system back up using this battery pack. This eliminates the need for a boost / backup power switch and battery isolator. This needs to be built and installed.
I am still trying to figure out how to make the alternator charge the battery without damaging it but have been unable to find a cost-effective and simple method. Stay tuned.
Why not leave the alternator working charging the start battery bank coach starting, engine, lights & dash loads. Separate system drains, keep a Trik L Start, eliminate isolator or remove house battery cable from isolator.
Out of that battery pack you got 400ah? ONLY ,
Using it 4 the start? What about the house batter how much ah?
I read through this thread for the first time today, and though I don't fully follow the purpose of your project, I do have a simple and cost-effective method to have the alternator charge your battery while driving down the road.
Hook the alternator up to small lead acid battery (a lawn tractor battery would be good) and then use that to power the ICharger 4010Duo (input 9-50 VDC).
The purpose is a technology proof-of-concept. To have a deep cycle, maintenance-free, efficient, light weight, dual power source ( Engine and House backup) that will last 20 years. By the way, alternators are only about 25% efficient, vs 80% using this new setup. That said, this technology has been around for over 10 years, is well understood, and should be viable for the next 20 years.
There are two possibilities:
1. BMS Method
Use a small lead 7AH AGM battery as a buffer. Then charge the 400AH directly, using the Orion BMS as the charge controller.
The alternator output line could be disconnected with a relay to shut off charge. The little AGM battery would remain connected to smooth out voltage and current. This little AGM is good for 70 A peak for 10 seconds.
This would be a fully automatic solution.
2. i Charger Method
Use a small lead 7AH AGM battery and alternator as a buffer and power source for the iCharger. . Then charge the 400AH LIFEPO4 using the iCharger as the charge controller. The iCharger power source could be fed either from the IOTA 14 Volt source or the alternator using simple diode switches.
Questions:
1. Which method is better?
2. Would the sudden change of current damage the alternator diodes or voltage regulator?
Switching a relay could cause the alternator output current to change from 30 amps to 1 amp in 20 miliseconds. That said, turning the incandescent headlights on the rig causes at least 100 A of inrush current and the alternator seems to be fine with that.
3. Could this modification make for a one-of-a-kind, unmaintainable white elephant? Let me answer my own question: Yes. I am concerned about this. Who would want a 1997 U270 with with full lithium technology?
Not sure if this will help you to achieve your goals but might be worth investigating:
LiFePO4 Battery Isolation Manager - Battle Born Batteries (https://battlebornbatteries.com/shop/lifepo4-battery-isolation-manager/)
RV Lithium/AGM Battery & Electrical System Upgrade - Part 1 - Intro (http://www.thervgeeks.com/electrical/lithium-agm-battery-electrical-upgrade-1/)
watch the series.. nice battery by Xantrex.. couldnt find costs but in the series they do tackle charging of the lithium and the agm separately
Does anyone have experience with what might happen if the U270 alternator charged a small 7AH AGM battery? A possible way to charge the 400AH LIFEPO4 battery with the alternator is to connect the alternator to a small AGM battery, then charge the lithium battery with the intelligent charger (iCharger 4010 Duo). These questions arise:
1. Too much current for the battery?
These small batteries are only supposed to be charged at 2 Amps max. Would the regulator handle that?
2. Too little current for the alternator?
Could the lack of a big battery cause the diodes to burn out?
Would the voltage regulator prevent this?
3. Too much three-phase ripple on the battery terminals?
Especially if I put a 30 Amp load on this small battery.
4. What if I connect a huge capacitor (5 Farads) in parallel with the small battery.
Would it smooth the ripple? Would the regulator be able to control the voltage properly?
Any advice would be appreciated.
LiFePO4 Battery Isolation Manager - Battle Born Batteries (https://battlebornbatteries.com/shop/lifepo4-battery-isolation-manager/)
With that help? That series I posted has some info that might or might not help ^.^d
That did not help. I need a device that prevents:
1. Alternator charge overcurrent, user settable current control.
This would prevent high alternator belt load and temperature.
2. Alternator damage (no sudden disconnects) using it's voltage feedback input. I currently don't have access to the field input.
This may require a surrogate battery to act as the alternator load / voltage smoothing device.
3. Battery damage. Needs a BMS "battery full" input.
I have reviewed Victron's offerings including their Buck Boost box. Does not do everything I need and costs a lot.
I have no idea what you are doing , but I often charge small batteries with large systems through a series of bulbs . They limit the total current .